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Carrier Accumulation in Organic Heterojunctions Controlled by Polarization

We present a heterojunction theory of ultrathin organic multi-layered devices, which is the revision of our previous work. Their characteristic feature is the generation of conductive space charge region in the insulating neutral dielectric region under the bias voltage application, while the insulating space charge region is generated in the conductive neutral region in the case of semiconductors. We propose the concept of quasiconductor to describe these features. From the theory, the capacitor equation of mobile carriers is given, which is an equivalent equation of the Mott-Schottky equation in semiconductor physics. Because the organics are dielectrics, the dynamics are controlled cleverly by polarization. The theory gives a relation among the applied voltage, carrier accumulation, mobility, and carrier density, which enables the in-situ simultaneous evaluation of mobility and the carrier density of ultrathin organic multi-layered devices. The concept of quiasiconductor is a missing link between organic electronics and the semiconductor physics.